Google Hacks 2Nd Edition [Electronic resources] نسخه متنی

Hack 47. Bring the Google Calculator to the Command Line

Perform feats of calculation on the command
line, powered by the magic of the Google calculator .

Everyone, whether they

admit it or not, forgets how to use the
Unix dc command-line calculator a few moments
after they figure it out for the nth time and stumble through the
calculation at hand. And, let's face it, the default
desktop (and I mean computer desktop ) calculator
usually doesn't go beyond the basics: add, subtract,
multiply, and divideyou'll have some grouping
ability with clever use of M+, M-, and MR, if you're
lucky.

What if you're interested in more than simple math?
I've lived in the U.S. for years now and still
don't know a yard from three feet (I know now,
thanks to the Google Calculator), let alone converting ounces to
grams or stone to kilograms.

This two-line PHP script by Adam

Trachtenberg
(http://www.trachtenberg.com)
brings the Google calculator to your command line so that you
don't have to skip a beator open your
browserwhen you just need to calculate something quickly.

2.29.1. The Code

The script uses PHP (http://www.php.net), better known as a web
programming and templating language, on the command line, passing
your calculation query to Google, scraping the returned results, and
dropping the answer into your virtual lap.

This hack assumes that you have PHP installed on your computer and it lives in the /usr/bin directory. If PHP is somewhere else on your system, you should alter the path on the first line accordingly (e.g., #!/usr/local/bin/php4 ).

#!/usr/bin/php
<?php
preg_match_all('{<b>.+= (.+?)</b>}',
file_get_contents('http://www.google.com/search?q=' .
urlencode(join(' ', array_splice($argv, 1)))), $matches);
print str_replace('<font size=-2> </font>', ',',
"{$matches[1][0]}\n");
?>

Save the code to a file called calc in your path
(I keep such things in a bin in my home
directory) and make it available to run by typing chmod +x
calc.

2.29.2. Running the Hack

Invoke your new calculator on the command line ["How
to Run the Scripts" in the Preface] by typing
calc (or ./calc if
you're in the same directory and
don't feel like fiddling about with paths) followed
by any Google calculator query that you might run through the regular
Google web search interface.

Here are a few examples:

% calc "21 * 2"
42
% calc 26 ounces + 1 pint in ounces
42 US fluid ounces
% calc pi
3.14159265
% calc answer to life, the universe and everything
42 If your shell gives you a parse error or returns garbage, try placing
the calculation inside quotation marks. For example, calc 21
* 2, without the double-quotes in the previous example,
returns $int($<b>calc.

There's absolutely no error checking in this hack, so if you enter something that Google doesn't think is a calculation, you'll likely get garbage or nothing at all. Likewise, remember that if Google changes its HTML output, the regular expression could fail; after all, as we'll point out several times in this book, scraping web pages is a brittle affair. That said, if this were made more robust, it'd no longer be a hack, now would it?